1. Field
This disclosure relates to acoustic metamaterial that exhibits negative-valued effective mass density and effective bulk modulus in an overlapping frequency regime.
2. Background
Acoustic metamaterials are man-made structures that aim to achieve acoustic/elastic properties which are not available in tradition materials. In particular, negativity in effective dynamic mass density was demonstrated in various different designs. Materials with negative acoustic properties present a negative mass density and bulk modulus, and therefore a negative index of refractivity. Negative effective bulk modulus was also realized in fluid channels with cavity resonators. Other effects such as focusing, image magnifying, acoustic cloaking, total absorption were also realized experimentally. Currently, simultaneous negativity in both effective mass density and bulk modulus was only achieved by a composite structure of membranes and pipe with side-holes.
Current panels do not offer simultaneous negative-valued effective mass density and bulk modulus in acoustics. An existing recipe for acoustic double negativity relies on coupling of two resonating structures. Additionally, a chain of unit cells is required for the demonstration of sufficient effect. Finally, the side-shunting holes are a significant source of dissipation.